Filament connection for electric lamps



March 1963 J. J. ZECCA ETAL 3,082,349

FILAMENT CONNECTION FOR ELECTRIC LAMPS Filed March 18, 1960 FIG. I.

INVENTORS.

JOHN J: 25609 "a b47172)? J7 DEC/r52. B

AGENT United States Patent M FILAMENT CONNECTION FOR ELECTRIC LAMPS John J. Zecca, Belleville, and Walter J. Decker, North Bergen, N.J., assignors to Westinghouse Electric Corporatiou, East Pittsburgh, Pa., a corporation of Pennsylvauia Filed Mar. 18, 1960, Ser. No. 15,856 6 Claims. (Cl. 313-271) This invention relates to electric lamps and, more particularly, to an improved filament connection for a flashing incandescent lamp.

Recently there has been developed and marketed a so-called flashing incandescent lamp wherein the filament is intermittently energized and de-energized by means of a bimetallic element that is attached directly to one end of the filament and adapted, in response to changes in the filament temperature, to switch the filament into and out of the circuit. The bimetallic member is in the form of a flat strip that is free to flex and is so disposed that when thermally actuated it makes-andbreaks contact with one of a pair of lead-in conductors sealed into the lamp. The other end of the filament is connected to the other of said conductors and the filament is thus periodically lighted by the action of the bimetal to produce a scintillatnig or flashing effect that is useful in decorative lighting and for warning and advertising purposes. A lamp of the aforesaid character and the resultant advantages over the prior art flashing arrangements are described in detail in US. Patent No. 2,901,667 dated August 25, 1959.

For reasons of economy and simplicity of construction the filament is connected to the free end of the bimetallic strip by means of a clamp that is formed on the end of the strip and closed around the filament. While this type of connection efiects the juncture of the aforesaid members without soldering or welding, it presents a serious problem in that the bimetallic clamp tends to flex and open up when cooled or heated, depending upon whether the end of the strip is bent toward the side of the bimetal that has the higher or lower coefficient of expansion. As a result, the filament gradually becomes loose within the clamp as the latter flexes with changes in temperature and may eventually drop out of the clamp and render the lamp inoperative.

It is accordingly the general object of the present invention to provide a flashing incandescent lamp that can be economically manufactured and will have a long useful life.

A more specific object is the provision of a connection joining the filament and bimetallic element of a flashing incandescent lamp or the like which can be quickly and inexpensively fabricated and maintains the aforesaid members securely interlocked one with another throughout the useful life of the lamp.

A better understanding of the invention will be obtained by referring to the accompanying drawing wherein:

FIG. 1 is a perspective view of a flashing incandescent lamp that incorporates the improved filament connection of this invention;

FIG. 2 is a perspective view on a greatly enlarged scale of the bimetallic member and associated portions of the filament and lamp stem;

FIG. 3 is an enlarged plan view of the filament connection shown in FIG. 2, a part of the bimetallic clamp being broken away to illustrate the manner in which the filament is partly collapsed by and locked within the clamp;

FIGS. 4 and 5 are plan views illustrating the initial and final steps, respectively, in closing and crimping the 3,082,349 Patented Mar. 19, 1963 2 bimetallic clamp with a pair of specially shaped jaws in accordance with this invention;

FIGS. 6 and 7 are plan views of other types of clamps according to the invention; and

FIG. 8 is a view corresponding to FIG. 5 but illustrates another type of clamping apparatus and clamp configuration.

While the invention may be advantageously employed to join various types of elements one of which is heat sensitive, it is especially adapted for use in connecting the bimetallic member of a flashing incandescent lamp to the filament thereof and has accordingly been so illustrated and will be so described.

In FIG. 1 there is shown a flashing incandescent lamp 10 which comprises an envelope 11 having a filament 12 sealed therein that is supported in thedesired configuration by a plurality of supports 18, a lead-in conductor 20 and a bimetallic member 22. The aforesaid supports and bimetallic member are embedded in and insulated from one another by a button 14 formed on the end of a vitreous support such as a re-entrant glass stem 16. As shown, the filament 12 is connected at one end to the lead-in conductor 20 and at its opposite end to the bimetallic member 22 which member is normally disposed in pressure contact with another lead-in conductor 24. Both of the aforesaid conductors are, in turn, sealed through the stem 16 and connected with a base 26 attached to the sealed end of the envelope 11. As shown more clearly in FIG. 2, the bimetallic member 22 comprises a fiat strip of dissimilar metals such as a layer of nickel-steel alloy known in the art as Invar and a layer of copper or silver, which layers are bonded together. The bimetallic strip is disposed in heat-receptive relationship with the filament 12 and is adapted in re sponse to changes in the temperature thereof to flex and intermittently connect the filament to the lead-in conductor 24, thereby periodically completing the circuit and producing the desired flashing of the filament. Flashing incandescent lamps of this type are well known in the art and are described in detal in the aforesaid US. Patent No. 2,901,667.

As shown in FIG. 2, the filament .12 is connected to the i imetallic member 22 by means of a flat clamp that is closed around and firmly grips the end of the filament. The aforesaid clamp is formed by bending the free end of the bimetallic strip back upon itself into a hook of the proper dimensions that is of U-shaped configuration when closed. Since the clamp 28 is fabricated from bimetallic material it is heat sensitive and inherently tends to open up when heated or cooled. It will tend to open when heated if the end of the bimetal strip is bent toward the metal layer that has the higher coefficient of expansion, that is, if the clamp 28 is formed in a manner such that the higher coefiicient metal comprises the inner surface of the clamp. conversely, if the relationship of the metal layers is reversed or if the end of the strip is bent in the opposite direction, then the high expansion metal will form the outer surface of the clamp and the latter will close tightly when heated and tend to open up when cooled. In either case, the clamp 28 flexes with changes in temperature and tends to open up thereby enabling the filament 12 to work free and even eventually fall out of the clamp resulting in premature failure of the lamp.

The aforesaid diflicu'lty is very conveniently and inexpensively remedied according to the present invention by deforming or crimping the clamp 28 either during or after it is closed around the inserted section of the filament 12. More specifically, the clamp .28 (as shown in FIGS. 2 and 3) is deformed to provide an indent or groove 30 in one of its faces and a protuberance or rib 32 in its opposite face, said groove and rib being aligned one with another 

1. A FILAMENT CONNECTION COMPRISING A WIRE FILAMENT, AND A BIMETALLIC MEMBER HAVING A FLAT CLAMP FORMED AT ONE END THAT IS CLOSED AROUND AND GRIPS SAID FILAMENT, SAID CLAMP HAVING A DEFORMATION IN AT LEAST ONE OF ITS EXTERIOR FACES THAT EXTENDS TRANSVERSELY OF THE CLAMPED-IN SECTION OF SAID FILAMENT AND LONGITUDINALLY OF SAID CLAMP AND THEREBY RIGIDIFIES SAID CLAMP AND PREVENTS IT FROM OPENING UNDER VARYING TEMPERATURE CONDITIONS, WHEREBY SAID CLAMP IS RENDERED LESS SENSITIVE TO VARIATIONS IN TEMPERATURE AND IS MAINTAINED IN MECHANICAL AND ELECTRICAL ENGAGEMENT WITH SAID FILAMENT EVEN WHEN THE LATTER IS ENERGIZED. 